ipheth: Properly distinguish length and alignment in URBs and skbs

commit 9c412942a0bb19ba18f7bd939d42eff1e132a901 upstream.

The USB protocol this driver implements appears to require 2 bytes of
padding in front of each received packet.  This used to be equal to
the value of NET_IP_ALIGN on x86, so the driver abused that constant
and mostly worked, but this is no longer the case.  The driver also
mixed up the URB and packet lengths, resulting in 2 bytes of junk at
the end of the skb.

Introduce a private constant for the 2 bytes of padding; fix this
confusion and check for the under-length case.

Signed-off-by: Ben Hutchings <bhutchings@solarflare.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

diff --git a/drivers/net/usb/ipheth.c b/drivers/net/usb/ipheth.c
index 7d42f9a2c06868027ac77c6265c76f9ce2288c27..81126ff85e0576e40b4d01aaf404044ffacfe1df 100644 (file)
--- a/drivers/net/usb/ipheth.c
+++ b/drivers/net/usb/ipheth.c
@@ -65,6 +65,7 @@
 #define IPHETH_USBINTF_PROTO    1
 
 #define IPHETH_BUF_SIZE         1516
+#define IPHETH_IP_ALIGN                2       /* padding at front of URB */
 #define IPHETH_TX_TIMEOUT       (5 * HZ)
 
 #define IPHETH_INTFNUM          2
@@ -202,18 +203,21 @@ static void ipheth_rcvbulk_callback(struct urb *urb)
                return;
        }
 
-       len = urb->actual_length;
-       buf = urb->transfer_buffer;
+       if (urb->actual_length <= IPHETH_IP_ALIGN) {
+               dev->net->stats.rx_length_errors++;
+               return;
+       }
+       len = urb->actual_length - IPHETH_IP_ALIGN;
+       buf = urb->transfer_buffer + IPHETH_IP_ALIGN;
 
-       skb = dev_alloc_skb(NET_IP_ALIGN + len);
+       skb = dev_alloc_skb(len);
        if (!skb) {
                err("%s: dev_alloc_skb: -ENOMEM", __func__);
                dev->net->stats.rx_dropped++;
                return;
        }
 
-       skb_reserve(skb, NET_IP_ALIGN);
-       memcpy(skb_put(skb, len), buf + NET_IP_ALIGN, len - NET_IP_ALIGN);
+       memcpy(skb_put(skb, len), buf, len);
        skb->dev = dev->net;
        skb->protocol = eth_type_trans(skb, dev->net);